I'm really not sure about this theory!!!
Here is what I've found ( I copied/pasted it from www.obgyn.net/fetal-monitoring/)
Table one showed that the incidence of male fetuses in relation with right
lateral placenta was 99.1% followed by fundal lateral anterior at 98.7% then by
fundal right lateral posterior placenta at 98.5%, then by anterior right lateral
placenta at 97.4%, and by the posterior right lateral placenta at 96.2%. The
overall average of this incidence was 97.25% for male fetuses and this is very
Table two showed that the incidence of female fetuses in relationship with the
fundal left lateral anterior was 98.7% followed by fundal left lateral posterior
at 98.6%, then by left lateral placenta at 98.5%, then by anterior left lateral
placenta at 97.7% and by the posterior left lateral placenta at 96.8%. The
overall average of this incidence was 97.5% and it is very significant. This
result might influence fetal gender if the IVF implantation was directed
accordingly to the specific site for the specific gender desired.
Maybe your boys were in these 2,75% of "girl position" placenta? I really want to know if U/S pics are mirrored.....I *think* they should have some sort of mark for right and left, not sure though.....